1. Field of the Invention
This invention relates to a plasma display panel, and more particularly to a plasma display panel that is capable of preventing miss-writing and improving discharge and light-emission efficiencies. The present invention also is directed to a method and apparatus for driving the plasma display panel.
2. Description of the Related Art
Generally, a plasma display panel (PDP) radiates a fluorescent body by an ultraviolet with a wavelength of 147 nm generated during a discharge of He+Xe or Ne+Xe gas to thereby display a picture including characters and graphics. Such a PDP is easy to be made into a thin-film and large-dimension type. Moreover, the PDP provides a very improved picture quality owing to a recent technical development. Particularly, since a three-electrode, alternating current (AC) surface-discharge PDP lowers a voltage required for a discharge by utilizing wall charges accumulated in the surface thereof upon discharge and protects electrodes from a sputtering generated by the discharge, it has advantages of low-voltage driving and long life.
Referring to FIG. 1, a conventional three-electrode, AC surface-discharge PDP includes a scanning electrode Y and a sustaining electrode Z provided on an upper substrate 10, and a data electrode X provided on a lower substrate 18. The scanning electrode Y and the sustaining electrode Z have transparent electrodes 12Y and 12Z with a large width and metal bus electrodes 13Y and 13Z with a small width, respectively, and are formed on the upper substrate in parallel. Since the metal bus electrodes 13Y and 13Z reflects a light to deteriorate a contrast, light-shielding layers 15Y and 15Z are provided between the metal bus electrodes 13Y and 13Z and the upper substrate 10 as shown in FIG. 2. The light-shielding layers 15Y and 15Z absorb a light going into the metal bus electrodes 13Y and 13Z via the upper substrate 10.
An upper dielectric layer 14 and a protective film 16 are disposed on the upper substrate 10 in such a manner to cover the scanning electrode Y and the sustaining electrode Z. Wall charges generated upon plasma discharge are accumulated in the upper dielectric layer 14. The protective film 16 prevents a damage of the upper dielectric layer 14 caused by a sputtering during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film 16 is usually made from magnesium oxide (MgO).
The data electrode X is perpendicular to the scanning electrode Y and the sustaining electrode Z.
A lower dielectric layer 22 and barrier ribs 24 are formed on the lower substrate 18. The surfaces of the lower dielectric layer 22 and the barrier ribs 24 are coated with a fluorescent material layer 26. The barrier ribs 24 separate adjacent discharge spaces in the horizontal direction to thereby prevent optical and electrical crosstalk between adjacent discharge cells. The fluorescent layer 26 is excited by an ultraviolet ray generated during the plasma discharge to generate any one of red, green and blue visible light rays. An inactive mixture gas of He+Xe or Ne+Xe is injected into a discharge space defined between the upper and lower substrate 10 and 18 and the barrier rib 24.
Such a three-electrode AC surface-discharge PDP drives one frame, which is divided into various sub-fields having a different discharge frequency, so as to realize gray levels of a picture. Each sub-field is again divided into a reset interval for uniformly causing a discharge, an address interval for selecting the discharge cell and a sustaining interval for realizing the gray levels depending on the discharge frequency.
For instance, when it is intended to display a picture of 256 gray levels, a frame interval equal to ( 1/60) second (i.e. 16.67 msec) is divided into 8 sub-fields SF1 to SF8. Each of the 8 sub-fields SF1 to SF8 is again divided into a reset interval, an address interval and a sustaining interval. The reset interval and the address interval of each sub-field are equal every sub-field. The address discharge for selecting the cell is caused by a voltage difference between the data electrode X and the scanning electrode Y. The sustaining interval is increased at a ratio of 2n (wherein n=0, 1, 2, 3, 4, 5, 6 and 7) at each sub-field. A sustaining discharge frequency in the sustaining interval is controlled at each sub-field in this manner, to thereby realize a gray scale required for a picture display. The sustaining discharge is generated by a high voltage of pulse signal applied alternately to the scanning electrode Y and a sustaining electrode Z.
FIG. 3 illustrates driving waveforms of the three-electrode AC surface-discharge PDP.
Referring to FIG. 3, in the reset interval, a reset discharge for initializing the discharge cell is generated by a reset pulse Vr applied to the sustaining electrode Z. Such a reset pulse Vr may be applied to the scanning electrode Y.
In the address interval, a scanning pulse—Vsc is sequentially applied to the scanning electrode Y and a data pulse Vd synchronized with the scanning pulse—Vsc is applied to the data electrode X. An address discharge is generated at the discharge cell supplied with the data pulse Vd. A low-level positive direct current voltage is applied to the sustaining electrode Z so as to prevent an erroneous discharge from being generated between the data electrode X and the sustaining electrode Z.
In the sustaining interval, a sustaining pulse Vs are alternately applied to the scanning electrode Y and the sustaining electrode Z. Then, the discharge cells selected by the address discharge generates a sustaining discharge continuously whenever the sustaining pulse Vs is applied.
Since such a three-electrode, AC surface-discharge PDP has the scanning electrode Y and the sustaining electrode Z positioned at the upper center of the discharge space, it has a low utility of the discharge space. For this reason, in the three-electrode, AC surface-discharge PDP, a voltage for causing a sustaining discharge and a power consumption are high while discharge and light-emission efficiencies during the sustaining discharge are low. More specifically, the sustaining discharge takes a surface discharge between the scanning electrode Y and the sustaining electrode Z. However, since the scanning electrode Y and the sustaining electrode Z concentrate at the center of the cell to lower a discharge-initiating voltage, a discharge path becomes short to cause low discharge and light-emission efficiencies. When allowing a distance between the scanning electrode Y and the sustaining electrode Z to be enlarged so as to raise the efficiencies, a discharge-initiating voltage becomes high in proportion to a distance between the two electrodes. Furthermore, when allowing an electrode width of at least one of the scanning electrode Y and the sustaining electrode Z to be widened, power consumption rises due to an increase in discharge current.
In order to solve the problems of the three-electrode, AC surface-discharge PDP, there has been suggested a five-electrode PDP in which an electrode for causing a sustaining discharge is divided into four electrodes.
Referring to FIG. 4 and FIG. 5, the conventional five-electrode PDP includes first and second trigger electrodes TY and TZ provided on an upper substrate 30 in such a manner to be positioned at the center of a discharge cell, first and second sustaining electrodes SY and SZ provided on the upper substrate 30 in such a manner to be positioned at the edge of the discharge cell, and a data electrode X provided at a lower substrate 40 in such a manner to be perpendicular to the trigger electrodes TY and TZ and the sustaining electrodes SY and SZ.
The trigger electrodes TY and TZ and the sustaining electrodes SY and SZ include transparent electrodes having a large width and metal bus electrodes having a small width, respectively, and are formed on the upper substrate 10 in parallel. The trigger electrodes TY and TZ can be easily discharged at a low potential difference because a distance Ni between the electrodes is small. The first trigger electrode TY also plays a role to cause an address discharge by a voltage level difference between an applied scanning pulse and a data pulse applied to the data electrode X. The sustaining electrodes SY and SZ are set to have a large distance Wi between the electrodes with having the trigger electrodes TY and YZ therebetween. The sustaining electrodes SY and SZ causes a long-path discharge by utilizing space charges and wall charges formed by a discharge between the trigger electrodes TY and TZ.
An upper dielectric layer 36 and a protective film 38 are disposed on the upper substrate 30 in such a manner to cover the trigger electrodes TY and TZ and the sustaining electrodes SY and SZ. Wall charges generated upon plasma discharge are accumulated in the upper dielectric layer 36. The protective film 38 prevents a damage of the upper dielectric layer 36 caused by a sputtering during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film 38 is usually made from magnesium oxide (MgO).
A lower dielectric layer 44 and barrier ribs 46 are formed on the lower substrate 40. The surfaces of the lower dielectric layer 44 and the barrier ribs 46 are coated with a fluorescent material layer 48. The barrier ribs 46 separate adjacent discharge spaces in the horizontal direction to thereby prevent optical and electrical crosstalk between adjacent discharge cells. The fluorescent material layer 48 is excited by an ultraviolet ray generated during the plasma discharge to generate any one of red, green and blue visible light rays. An inactive mixture gas of He+Xe or Ne+Xe is injected into a discharge space defined among the upper and lower substrate 30 and 40 and the barrier ribs 46.
Like the three-electrode PDP, such a five-electrode AC surface-discharge PDP drives one frame, which is divided into various sub-fields having a different discharge frequency, so as to realize gray levels of a picture. This will be described in detail in conjunction with FIG. 6 and FIG. 7.
FIG. 6 and FIG. 7 show a configuration of a trigger/sustaining driving apparatus for the five-electrode PDP and output waveforms thereof, respectively.
Referring to FIG. 6, the driving apparatus for the five-electrode PDP includes a first sustaining driver 58 for driving a first sustaining electrode SY, a first trigger driver 56 for driving the first trigger electrode TY, a second sustaining driver 62 for driving the second sustaining electrode SZ, and a second trigger driver 60 for driving the second trigger electrode TZ.
The first sustaining driver 58 applies a negative direct current (DC) voltage to the first sustaining electrode SY in the address interval and thereafter applies a sustaining pulse to the first sustaining electrode SY in the sustaining interval. The first trigger driver 56 applies a negative scanning pulse to the first trigger electrode TY in the address interval and thereafter applies a sustaining pulse to the first trigger electrode TY in the sustaining interval. The second sustaining driver 62 applies a positive DC voltage to the second sustaining electrode SZ in the sustaining interval and thereafter applies a sustaining pulse to the second sustaining electrode SZ in the sustaining interval. The second trigger driver 60 applies a reset pulse to the second trigger electrode TZ in the reset interval and thereafter applies a positive DC voltage to the second trigger electrode TZ in the address interval. Further, the second trigger driver 60 applies a sustaining pulse to the second trigger electrode TZ.
In the mean time, the data electrode X receives a data pulse synchronized with a scanning pulse from a data driver (not shown).
Referring now to FIG. 7, in the reset interval, a positive reset pulse Vrst having a high voltage level is applied to the second trigger electrode TZ. Then, the discharge cells at the entire field are reset-discharged to be initialized while creating a uniform amount of wall charge. The data electrode X is supplied with a positive pulse signal having a low voltage level to prevent an erroneous discharge from being generated between the second trigger electrode TZ and the data electrode X.
In the address interval, a scanning pulse—Vsc is sequentially applied to the first trigger electrodes TY. The data electrodes for one horizontal line are simultaneously supplied with a data pulse Vd synchronized with the scanning pulse—Vsc. The discharge cell supplied with the data pulse Vd causes an address discharge by a voltage difference between the data electrode X and the first trigger electrode TY and an internal wall voltage.
In the sustaining interval, a trigger pulse Vt and a sustaining pulse Vs are simultaneously applied to the first trigger electrode TY and the first sustaining electrode SY, respectively. Also, the trigger pulse Vt and the sustaining pulse Vs are simultaneously applied to the second trigger electrode TZ and the second sustaining electrode SZ, respectively. Herein, a voltage level of the trigger pulse Vt is set to be lower than that of the sustaining pulse Vs. When a first trigger pulse Vt is applied to the first trigger electrode TY, the discharge cells having generated the address discharge cause a short-path discharge between the first trigger electrode TY and the second trigger electrode TZ. By this short-path discharge, space charges and wall charges are created within the discharge cells selected by the address discharge. The space charges and the wall charges created by the short-path discharge provide a priming effect with respect to a long-path discharge between the first and second sustaining electrodes SY and SZ. In other words, the priming effect caused by the short-path discharge induces a long-path discharge between the first and second electrodes SY and SZ. In other words, the short-path discharge between the trigger electrodes TY and TZ can cause a long-path discharge between the sustaining electrodes SY and SZ having a wide distance between electrodes at a low voltage.
In the five-electrode PDP, the sustaining discharge is made at a long path to increase a quantity of ultraviolet rays generated by the discharge. Thus, a light-emission quantity of the fluorescent material 48 excited by the ultraviolet rays is increased to that extent, to thereby provide discharge and light-emission efficiencies higher than the three-electrode PDP.
However, in the conventional five-electrode PDP, since the first trigger electrode TY has a small width, it is difficult to accumulate a sufficient amount of wall charges into the first trigger electrode TY upon address discharge. If an amount of wall charges created upon address discharge is small, then an external application voltage required for a sustaining discharge is raised to that extent. As a result, the conventional five-electrode PDP has large power consumption and fails to obtain a satisfying discharge efficiency.
Furthermore, since the conventional five-electrode PDP fails to form sufficient wall charges upon address discharge, it has a problem of miss-writing in that a sustaining discharge does not occur.
In addition, in the conventional five-electrode PDP, since a voltage level of the trigger pulse Vt is different from that of the sustaining pulse Vs, the trigger pulses TY and TZ and the sustaining pulses SY and SZ should be driven individually. Thus, the conventional five-electrode PDP has a problem in that it has a complicated driving circuitry and a large manufacturing cost.